Google was close to a deal to get Facebook user data into its search engine back in 2009, but talks broke down over privacy concerns and fear that Google would use Facebook's data to help build a competing social network.

According to an unnamed source "on Facebook's side of the negotiations," Facebook wanted to make sure that users' privacy settings were fully respected.

For instance, if you put your phone number on your Facebook profile and share it only with your friends, Facebook wanted to make sure that phone number would show up only when your friends ran Google searches -- not for broader searches conducted by everybody in the world.

Google said that for technical reasons, they couldn't do this. So Facebook said no deal.

The irony, as Battelle points out: Google is using EXACTLY this kind of privacy protection for data from Google+ in search results.

That doesn't necessarily mean Google was lying. Google+ was built with granular privacy settings in mind -- that's the whole point of the Circles you can create for friends, acquaintances, coworkers and so on. So Google probably had to revamp its search engine to figure out how to honor these privacy settings. That work may indeed have taken two years.

Reportedly, Facebook also wanted Google to sign an agreement saying it wouldn't use Facebook's data to build its own social network.

Here, Google's reluctance makes a lot of sense: it was already thinking about building its own social network, and it would have been very hard to prove that it didn't crib some ideas from Facebook.

Battelle's source also mentions that Microsoft was willing to agree to these terms for Bing, which is why they got a search deal when Google did not.